This document describes the user requirements on the smooth upgrade function of the NFVI and VIM with respect to the upgrades of the OPNFV platform from one version to another. Smooth upgrade means that the upgrade results in no service outage for the end-users. This requires that the process of the upgrade is automatically carried out by a tool (code name: Escalator) with pre-configured data. The upgrade process includes preparation, validation, execution, monitoring and conclusion.

The requirements are defined in a stepwise approach, i.e. in the first phase focusing on the upgrade of the VIM then widening the scope to the NFVI.

The requirements may apply to different NFV functions (NFVI, or VIM, or both of them). They will be classified in the Appendix of this document.

The objects being upgraded described in this document are software modules covered by red box in the picture below which includes: VIM and NFVI.

The target of the upgrade is to reduce the impact on the applications in the blue box below as much as possible.

Please keep in mind that the upgrade tool does not take Vi-Vnfm and Or-Vi into consideration. In other words, these two interfaces may not provided service normally during upgrade procedure.